INSECTS
INSECTS
INTERNAL SECTION OP THE HONEYBEE
flies were very fine. But the golden period of close observation and artistic illustration svas reached in the work of Lyonet (i 707—89). In 1760 was published his monograph on the minute anatomy of the larva of the willow
moth. He counted more than 4,000 muscles in the body of that tiny animal, and traced the branches of ne rve s and breathingtubes to individual muscles. It is unsurpassed as a piece of deli-L cate work, and his sketches are j as fine as any ever executed. Strauss-Durck-heim (1790-1865) comes next in succession. His monograph on the anatomy of the cockchafe r (1828) rivals that of Lyonet in accuracy and detail. He wrote under the influence of Cuvier, who had introduced the comparative method into anatomy, and he undertook to make insect anatomy comparative. Newport of England earned the work to a higher level, and began to observe the embryology of insects. Since his time much work has been done on their microscopic structure. Franz Leydig has been a pioneer and leader in this line, and his studies on the anatomy of sense-organs of insects are famous. The embryology of* insects has also been studied with success by a very large number of observers.
Insects are of interest to the naturalist from the standpoint of their structure, metamorphosis, embryology and classification. They are of importance to the agriculturist on account of the injuries they cause to crops, shade trees etc. "It has been calculated that insects about equally divide the produce of the soil with the farmer." Many states support a state entomologist to limit the ravages of injurious insects like the army worm, weevils, Hessian fly, locusts etc. (consult these topics). The simplest insects are worm-like and wingless, or with rudimentary wings, thus suggesting affinities between insects and worms. A very interesting form, named peripatus, has been discovered in Africa, Australia and South America that unites the two groups. This is a long-jointed animal resembling a worm externally, except that it has antennas and jointed legs. Internally it has breathing tubes, which belong to
insects as a class, and a pair of secreting tubes in each joint, except a few at the extremities. These tubes correspond to secreting tubes of worms.
Classification of Insects. Insects are grouped into orders, mainly according to the nature of their wings. It is estimated that there are about 300,000 species. They are so multitudinous that reference must be made to a textbook on entomology for any adequate treatment. Nevertheless, it will be convenient for the amateur student to have a means of recognizing the order to which any common insect belongs. It will be simpler to begin with the highest order of the class Insecta and pass downward:
IX: Hymenoptera, bees, wasps, ants, ichneumon flies and. others. Insects having four membranous wings with few cross veins. Mouth-parts formed for biting and sucking. The highest developed of insects in organization and intelligence. (See Lubbock, Ants, Bees and Wasps. See, also, ANT, BEE, ICHNEUMON FLIES, WASP etc.) VIII: Coleop-tera, beetles. Insects with hard wing-covers, the inner membranous pair used only for flying. This is the most numerous order, there being more than 11,000 species known in America north of Mexico, and the number in tropical regions is immense. (See BEETLE, CARPET-BEETLE, WEEVIL etc.) VII: Dip-tera, flies, gnats, midges and others. Two.-winged insects with mouth-parts formed for sucking. (See GNAT, HESSIAN FLY, MOSQUITO etc.) VI: Lepidoptera, butterflies, moths and others. Insects with four wings covered with overlapping scales. Mouth-parts formed for sucking. (See ARMY-
SWALLOW-TAIL BUTTERFLY
WORM, BUTTERFLY, CATERPILLAR, MOTH etc.) V: Neuroptera, ant-lion, dobson and others. Insects having four membranous wings with numerous veins. Mouth-parts formed for biting. Formerly the dragon-flies and others were included in this order, but the modern entomologists have split the old order into ten new ones. IV: Hemip-
